Major objectives for this year are: (1) Isolate, purify, and characterize the non-lysozyme bactericidal factor(s) from normal human plasma serum (NHPS) active against Bacillus subtilis. Our present approach, which has shown some degree of success, is to perform a batch adsorption of NHPS onto QAE-Sephadex A-50. The neutral and cationic proteins are collected by filtration through a sintered glass filter, and, after concentration are passed through a CM-Sephadex column. Elution with a shallow NaCl gradient results in clear separation of lysozyme from other bactericidal factor(s). Further purification of this material must await the gathering of added information regarding its general properties. (2) Isolate, purify and characterize the bactericidal factors active against B. subtilis and other gram positive bacteria from normal rabbit serum. This project is well under way. Of special interest will be the determination of the cellular source of these materials, as well as their mode of action. Preliminary data suggest that these bactericides may well function differently from those isolated from human serum.